Know These Key Differences Between Functional And Non-Functional Testing


Software Testing is extensively classified into Functional and Non-Functional Testing. Let us examine in detail these types of testing along with the precise distinctions between both functional and non-functional testing. Well-designed quality assurance techniques and plans commonly include both functional testing and non-functional testing. Hence, understanding the difference between functional and non-functional testing is significant for testing and QA teams. While both comprise a critical part of the application examination process, they serve very various objectives. 

What is functional testing? 

Functional testing is a kind of software testing that verifies features of a product that function according to prerequisites, recognizing all areas where performance doesn’t fulfill expected outcomes.

On the other hand, non-functional testing conducts checks on broader quality concerns, verifying all non-functional characteristics of the software application, for instance, performance, usability, compliance, etc.

This blog outlines the differences between the testing types of functional testing and types of non-functional testing moreover, delivering examples, strategies, and advice.

Functional and non-functional testing

Before we can recognize the difference between functional and non-functional testing, we require to understand the difference between functional and non-functional requirements:

Functional requirements define the behaviour or performance of the software system. Whereas, non-functional requirements, illustrate the execution or usability of the software system. While a functional prerequisite will specify that an element must enforce some action, a non-functional requirement might determine the speed with which the feature completes that action.

We can interpret that functional requirements can be defined by a single word i.e. ‘WHAT’ and nonfunctional requirements can be defined as ‘HOW’. So, the testing of functional requirements is the assurance that the software is implementing actions as they should, while nonfunctional testing assists verify that customer expectations are being fulfilled.

Functional testing strategies

There are a diversity of functional testing methods, and the adequate means to confirm functional test coverage is a combination of manual and automated testing.

The most popular functional testing strategies are black-box testing procedures, wherein the tester does not require to examine the internal source code but validates functionality by testing several input combinations. Here are some of the widespread functional testing techniques given below:

  1. Installation testing for mobile application or desktop, assessing proper installation
  2. Boundary value analysis in which  testing of the limitations of numerical inputs
  3. Equivalence partitioning where grouping tests jointly to decrease overlap of identical functional tests
  4. Error guessing, examining where functional problems are most likely to be found, and testing these more greatly than other areas
  5. Unit testing where testing is conducted at the minor level of the software, not how the system is functioning as a whole, but whether each unit is implementing properly or not
  6. API testing tests that internal and external APIs are functioning properly, comprising data transfer and authorization
  7. In regression testing, tests that are performed to verify that modern software changes did not have unfavourable effects on existing functionality i.e. most common automation strategy

All functional tests possess a particular output that is required of any input like if you enter valid information, then you expect the data to be accepted. All functional tests can be scripted with a very detailed pass or fail standards. Now let’s look at what is non-functional testing?

Functional and Non-Functional Testing Strategies

What is Non-functional testing?

Non-functional testing can occasionally need more technical expertise and creativity because you are testing what the consumer wants for an all-around quality experience and not X input directed to Y output. Let’s have a glimpse of the chief non-functional testing techniques:

  1. In load testing, tests executed on a simulated setting to examine the behaviour of the system during expected conditions of various number of users
  2. Stress testing, the testing operation when low on resources, such as server problems or lack of hard drive space on a device
  3. Scalability testing, checking a system’s capacity to scale with heightened usage and to what extent performance is affected
  4. In volume testing, testing performance with a high volume of data, not necessarily an increased number of users. However, could be one user performing a high-volume task, such as a multiple-file upload
  5. Security testing where tests performed to disclose how vulnerable the system is to attacks, and how adequately data is protected
  6. Disaster recovery testing reviews how shortly a system can recover following a crash or major problem
  7. In the compliance testing, tests of the software system against any set of standards whether due to industry regulations or a firm’s set of standards
  8. Usability testing – assessing whether the GUI is constant and if the application as a total is intuitive and easy to use

While some non-functional testing techniques can have a pass or fail criterion such as volume testing, whereas others can be more accurate and established on the belief of the tester like usability testing. Nonetheless, nonfunctional tests should be written to be quantifiable and measurable wherever possible.

Taking notice of customer feedback is necessary for updating non-functional requirements. While an industry might recognize certain scalability and security components during requirements gathering, customer feedback can broaden the set of checks to encompass better testing of how an app heals after a boom or how an app performs with the smallest storage space left on a device.

Customer feedback can assist with a risk examination for functional testing but is even more helpful to non-functional testing because the feedback can enable set the bar. Whereas with functional tests the bar is already established. Eventually, knowing the difference between these two types of tests can benefit during test planning, so that you are precise on what is being covered and why.

As we understand that testing is the most significant stage in the method of delivery of any application or software as it is just testing which not only substantiates the quality of an application but also furnishes an opportunity to the creator to enhance its product.

The entire application is being formulated as per the requirement of the customer or client so established on testing, the functionality of the application based on these requirements, and testing the performance and usability we can differentiate between Functional and Non-functional Testing.